In the field of tufting carpets, it has been known to tuft carpets having spaced rows of looped pile and cut pile tufts. A variety of techniques have been utilized to obtain cut and loop pile tufts in the same carpet pattern. For example, U.S. Pat. No. 3,919,953 discloses an apparatus and method for tufting spaced rows of loop pile and cut pile tufts formed in the backing material using a multi-needle tufting machine having two transverse rows of needles with each row cooperating with a series of loop pile loopers or cut pile loopers.
A variety of techniques have also been developed to form cut pile and loop pile stitches in the same row, as for instance by utilizing spring clips permitting loops of yarn to be withdrawn from a looper by backrobbing as described in U.S. Pat. Nos. 3,084,465; 4,155,319; and 4,522,132. A similar result has also been obtained through the use of pusher devices as in U.S. Pat. No. 4,320,711 to selectively push loops off the loopers before the loops are cut.
Level cut and loop pile has also been formed in the same rows of stitches as in U.S. Pat. Nos. 4,134,347; 4,185,569; 6,155,187 and 7,222,576 utilizing a gate structure. Gates are selectively opened and closed to promote passage of selected loops into the knife blade cooperating with the looper or hook.
The improvements to the design of Card, U.S. Pat. No. 3,199,953 have been numerous. The style of carpet created by this design is variously referred to as Precision Cut/Uncut™ or Velva Loop™. An initial improvement to this machine design having separate cutting and looping systems under the backing fabric, was the addition of a pattern yarn feed attachment to the yarns being fed to the needles associated with the looping attachment. This improvement permitted yarns to be fed at about three different rates using clutch scroll attachments to achieve variation in loop tuft heights. Today, with servo scroll and single end scroll attachments, loop patterning with precision height variation is possible. The loop patterning permits loops to be tufted at heights equal to or lower than the yarns being tufted by the needles associated with the cutting system. Tufting loops at heights greater than the yarns tufted by the needles associated with the cutting system frequently leads to loops being seized on the hooks and being cut or fouling the action.
A further improvement to the tufting machine design with separate cutting and looping systems under the backing fabric was added when a sculptured cutting apparatus as depicted in U.S. Pat. No. 4,557,209 was added to the cut pile side of the tufting machine. With this configuration, and utilizing a pattern control yarn feed, it became possible to slightly sculpt the height of the cut pile tufts. With pattern control yarn feed on the loop pile side, the heights of the loop pile tufts could also be varied.
Yet another improvement to the Precision Cut/Uncut™ or Velva Loop™ systems was the addition of spring clips on the cut side loopers or hooks. In this configuration, if the yarn to the needles on the cut pile side is fed in normal increments, the tufts are produced in cut pile at full height. However, if the yarn is backrobbed or highly tensioned, the loops pull off of the hooks before proceeding to the cutting zone. The backrobbing or yarn tension causes the loops to be formed from less yarn than the cut pile tufts. Thus, the hooks equipped with spring clips produce a combination of full height cut tufts and lower height loop tufts. By utilizing a pattern control yarn feed on the loop pile side together with hooks having spring clips on the cut pile side, it is possible to make patterns with loops tufted on the loop side lower than most of the low loops on the cut pile side. When the loop pile side loops are this low, effectively buried, the yarns from the cut side needles may be shown as either cut pile tufts or loop tufts. The yarns from the loop side needles may also be fed at higher rates and be shown as loops either concealing yarns from the cut side or allowing a portion of the cut side yarns to show.
The process of backrobbing or highly tensioning yarns so that yarn loops are removed from the hooks before proceeding to the cutting zone is not precisely controllable, largely due to the elasticity of yarns. Accordingly the hooks are usually set beneath the backing fabric so that the cut pile height is at least 5/16th inch and more commonly ⅜th inch. At this pile height, the spacing between the hooks and the backing fabric gives the yarn an instant to reduce its tension after a yarn loop is removed from a hook and lessens the possibility of the loop snapping through the backing. If a lower cut pile height is used, there is a likelihood that some tufts will be completely pulled out of the backing fabric by the yarn tension necessary to pull the yarn loops off of the hooks. A ⅜th inch pile height consumes more yarn than lower pile heights, and for many carpet designs is unnecessarily tall.
Therefore, it can be seen that a need exists for an improved method and system of forming cut and loop pile tufts on the cut side of tufting machine having separate cutting and looping systems below the backing fabric that addresses the foregoing and related problems in the art.